1. Field of the Invention
This invention relates to fire and heat resistant structural building elements and methods for their preparation.
2. Description of the Prior Art
Fire retardant building panels which employ a combination of gypsum or gypsum based plaster and a foamed plastic are well known. For example see, U.S. Pat. Nos. 3,295,278 and 3,462,399. Gypsum plaster formulations suitable for spray application are also well recognized in the building art, some including a bonding agent incorporated in the plaster mix, see U.S Pat. No. 3,819,388. A number of industrial bulletins disclose various types of fire retardant coating materials which are suitable for application directly to foamed plastics. Pertinent bulletins are listed herein: Amspec. Inc., 1880 MacKenzie Drive, Columbus, Ohio, Building Insulation Bulletin, September 1973, p. 5, discloses the application of gypsum plaster on polyurethane foam or styrofoam; CPR Division, The Upjohn company, 555 Alaska Ave., Torrance, Calif., Urethane Building Insulation Bulletin, June 1973 discloses the application of gypsum plaster upon urethane or isocyanurate foam; Tufcon Inc., 17000 S. Western Ave., P. O. Box 149, Gardena, Calif., Specification TUR-304 discloses the application of a portland cement based formulation in three separate coats on polyurethane foam which has been coated with a bonding material; Foamseal Inc., 2425 N. Lapeer Road, Oxford, Mich., Test Report, May 1974 discloses the application of Pyrocrete X 4800-11 which is a magnesium oxychloride cement, on polyurethane foam; Albi Manufacturing Corp., 98 East Main St., Rockville, Conn., Albi Product Data Sheet on Duraspray recommends the application of this magnesium oxygen chloride cement to exposed plastic foam insulation; and E. H. O'Neill Floors Company, Cicero, Ill., in Fire Ban for Insulation, disclose the use of the magnesium oxychloride composition Fire-Band over polyurethane insulation board.
However, the art has recognized that the application of such cementitious coatings directly to foamed insulation, without the use of some type of lath or wall tie, leads to adhesion problems, particularly in overhead applications. Also, as in the case of portland cement plaster, it must be applied in a number of thin coats to make up the desired thickness. The prior art coatings which contain magnesium oxychloride cannot be used without sealing coats in banana rooms, packing house chill rooms, meat sales coolers, and the like due to the hazard of corrosive materials which can arise from such coatings. See Fire Ban for Insulation, page 3, July 1961, E. H. O'Neill, Cicero, Ill.
It has now been found, unexpectedly, that gypsum plaster can be applied as a single coat of desired thickness to a plastic insulating foam layer which has received a coating of a bonding agent, to provide a strong and very useful structural building combination. Further, it has been found that the aforesaid elements in combination with various types of wall, ceiling, and floor members provide structural elements which possess excellent thermal insulation and fire resistant properties. In yet a further novel aspect of the present invention, it has been found that existing structural elements such as walls, roofs, etc. which may present a fire hazard due to exposed plastic foam thereon, can now be facilely and economically provided with a thermal barrier of the present invention thereby decreasing the hazard.